Infrared absorber and agricultural film

ABSTRACT

An infrared absorber which comprises containing as an effective ingredient a hydroxide complex salt represented by the formula 
     
       
         [Al 2 (Li (1−x) .+M 2+   (x+y)(OH)   (6+2y) ] n (A n− ) (1+x) .mH 2 O 
       
     
     (wherein M 2+  is a divalent metal, A n−  is an anion having a valence of n, and m, x and y are numbers respectively in the ranges of 0≦m&lt;5, 0.01≦x≦0.5 and 0≦y≦0.5), which has a high ability to absorp infrared rays and a refractive index close to that of the resin so that it has a good dispersibility with the resins when incorporated in the resin and the shaped film therefrom is excellent in the heat insulation property and transparency so that it is suitable as an agricultural film.

TECHNICAL FIELD

The present invention relates to an infrared absorber consisting of acomplex hydroxide salt which may be represented by the formula

[Al₂(Li_((1−x)).M²⁺ _((x+y))(OH)_((6+2y))]_(n)(A^(n−))_((1+x)).mH₂O

(wherein M²⁺ is a divalent metal, A^(n−) is an anion having a valence ofn, and m, x and y are numbers respectively in the ranges of 0≦m<5, 0.01≦x≦0.5 and 0≦y≦0.5) and an agricultural film prepared by incorporatingsaid infrared absorber into a resin and shaping the mixture into a film.

PRIOR ART

An agricultural film which is being used in a greenhouse cultivationsuch as growing in houses or tunnels is required to have characteristicproperties such that infrared rays radiated from the ground and plantsare prevented from being liberated outside the houses or tunnels by theabsorption, reflection, etc. during the night while the sunlight istransmitted efficently at a high transmission rate into the houses ortunnels during the daytime. It is known that the infrared rays radiatedat a high radiation rate from the ground and plants lie in wavelengthsranging from 5˜25 μm. It is required for the agricultural film to becapable of absorbing infrared rays having wavelengths from 5 to 25 μm,especially wavelengths in the vicinity of 10 μm which is the maximumradiation rate.

For the above agricultural film, magnesium carbonate, magnesiumsilicate, silicon dioxide, aluminum oxide, barium sulfate, calciumsulfate, magnesium hydroxide, aluminum hyroxide, calcium hydroxide,phosphates, silicates, hydrotalcites have been hitherto employed asinfrared absorbers.

However, these inorganic powders used hitherto have both respectivemerits and demerits, and none of them fully meets the above requirementsfor properties. For example, silicon dioxide and magnesium silicate areexcellent in the infrared absorptivity but have problems in therefractive index and dispersibility with the result that they impair thelight transmittance of film. Thus, they are not suitable for use as theagricultural film. Also, hydrotalcites are relatively excellent in thedispersibility and refractive index but they are not fully satisfactoryin infrared absorptivity.

Also, the Japanese Patent Kokai No. Hei 7-300313 discloses a technicsusing a lithium aluminum complex hydroxide salt as a heat insulationagent for an agricultural film. This hydroxide salt has a defect that itcauses a bad transparency because it has a refractive index of 1.55which is far apart from the value of about 1.50 that is the refractiveindex of polyolefin resin.

DISCLOSURE OF THE INVENTION

It is an object of the present invention to provide an infrared absorberand an agricultural film, said infrared absorber having a high abilityto absorb infrared rays and a good dispersibility when incorporated intoa resin, and a refractive index which is near to that of the resin sothat the film shaped therefrom has excellent heat insulation propertyand transparency.

As a result of having ardently studied to solve the above problems, thepresent inventors have found that the above problems may be solved by abasic complex hydroxide salt which may be represented by the followingformula (I)

[Al₂(Li_((1−x)).M²⁺ _((x+y))(OH)_((6+2y))]_(n)(A^(n−))_((1+x)).mH₂O  (I)

(wherein M²⁺ is a divalent metal, A^(n−) is an anion having a valence ofn, and m, x and y are numbers respectively in the ranges of 0≦m<5, 0.01≦x≦0.5 and 0≦y≦0.5) and which has a high ability to absorb infrared raysin the vicinity of 10 μm of wavelength and which has a basal skeletoncomposed of an aluminum hydroxide octahedron layer of the gibbsitestructure, and have completed the present invention.

That is, the present invention is an infrared absorber which ischaracterized by containing as an effective ingredient the complexhydroxide salt represented by the above formula (I) [hereinafter,referred to as the compound (I)]. The compound (I) of the presentinvention is one (in the case of y=0) which has a basic structurecomposed of a basal skeleton formed by entering lithium and divalentions into a vacant site of an aluminum hydroxide octahedron layer of thegibbsite structure and an interlayer wherein an anion is introduced.

Also, it is a complex hydroxide salt wherein a hydroxide of divalentmetal is entered into the basic structure (in the case of 0<y<1).Although this divalent metal is not limited particularly, Mg, Zn, Ca andthe like are preferred from the viewpoints that they may be easilyintroduced, have white color and meet transparency when incorporatedinto film.

A^(n−) represents a n-varent anion. Examples of anion include c rbonicacid, phosphoric, acid, silicic, acid, acetic acid, propionic acid,adipic acid, benzoic acid, phthalic acid, terephtharic acid, maleicacid, fumaric acid, citric acid, tartaric acid, succinic acid,p-hydrpxybenzoic acid, salicylic acid, picric acid, sulfuric acid,nitric acid, hydrochloric acid, iodine, fluorine, bromine and the like.Phosphoric acid, carbonic acid and silicic acid may be preferably used.

In the case that the infrared absorber of the present invention, that isthe infrared absorber which is characterized by containing as aneffective ingredient the compound (I) as above-mentioned is used to beincorporated into films such as agricultural film and so on, one havinga very fine particle, a high dispersibility and a relatively developedcrystal are preferred. Therefore, the average secondary particle size ispreferably below 3 μm, more preferably below 1 μm. Also, the BETspecific surface area is preferably below 50 m²/g, more preferably below20 m²/g.

The followings illustrate in detailes a process for preparing thecompound (I) of the present invention where M²⁺ is Mg as a specificexample.

The compound (I) of the present invention in the case of M²⁺ being Mgand y=0, a basic aluminum magnesium complex hydroxide of carbonate iontype [Al₂Li_((1−x)).Mg_((x))(OH)₆]_(n)(CO₃)_((1+x)).mH₂O may be preparedby the following process.

Aluminum hydroxide is reacted with lithium carbonate and carbonate ofmagnesium such as magnesium carbonate and basic magnesium carbonate inan aqueous medium under heat treatment.

Lithium carbonate and magnesium carbonate or basic magnesium carbonatemay be used in such a amount that [Li/Al₂O₃ (molar ratio)]+[MgO/Al₂O₃(molar ratio)] becomes 1 with respect to the content of Al₂O₃ inaluminum hydroxide. However, slight excess of lithium component may beadded.

A complex hydroxide salt (in the case of 0<y≦0.5) wherein magnesiumhydroxide is introduced may be prepared by reacting aluminum hydroxidewith lithium carbonate, carbonate of magnesium such as magnesiumcarbonate and basic magnesium carbonate and one or more of water solublemagnesium salts selected from the group consisting of magnesiumchloride, magnesium sulfate, magnesium nitrate and magnesium hydroxidein an aqueous medium under heat treatment. In this case too, lithiumcarbonate and magnesium carbonate or basic magnesium carbonate may beused in such a amount that [Li/Al₂O₃ (molar ratio)]+[MgO/Al₂O₃ (molarratio)] becomes 1 with respect to the content of Al₂O₃ in aluminumhydroxide. However, slight excess of lithium component may be added.

The temperature range for heat treatment is preferably an appropriatetemperature ranging from an ordinary temperature to 200° C., morepreferably 90˜160° C., most preferably 110˜160° C. In the case wheretreatment temperature is lower than the ordinary temperature, it is notpreferable because the extent of crystallinity becomes low.

The above complex metal hydroxide salt of carbonate ion type may betreated with acids, for example mineral acids such as nitric acid,halogenic acid such as hydrochloric acid, sulfuric acid and so on ororganic acids, for example monocarboxylic acid (monobasic organic acid)such as acetic acid, thereby the carbonate ion intercalated betweenlayers may be substituted by other anion. By selecting the startingmaterials properly the complex metal hydroxide salt of other anion typewhich may be obtained by the above treatment is converted into a basiclithium magnesium aluminum complex hydroxide salt wherein ionintercalated between the layers is halogen ion, nitric acid ion,sulfuric ion, monocarboxylic acid ion and so on without passing throughstep for the above basic lithium magnesium aluminum complex metalhydroxide salt of carbonate ion type.

The compound (I) of the present invention may be subjected tohydrothermal treatment using an autoclave and the like thereby BETspecific surface area and secondary particle size may be adjusted tosuitable range. The temperature range for hydrothermal treatment ispreferably 100˜200° C., more preferably 110˜160° C. The preparation ofother divalent metal than Mg with respect to M²⁺ may also be conductedin a similar manner as that of the Mg type and there is no particularcare to be taken for it.

The infrared absorber of the present invention may be surface-treatedwith a coating agent thereby excellent dispersibility may be achieved.As examples of coating agent there may be taken higher fatty acids,higher fatty acid salts, phosphoric esters of higher aliphatic alcohols,waxes, nonionic surfactants, cationic surfactants, coupling agent andthe like. Higher fatty acids, higher fatty acid salts, phosphoric estersof higher aliphatic alcohols, nonionic surfactants, cationic surfactantsor coupling agent are preferred.

As higher fatty acids, for example lauric acid, palmitic acid, oleicacid, stearic acid, capric acid, myristic acid and linoleic acid aretaken. As higher fatty acid salts, for example sodium or potassium saltof the above higher fatty acids are taken. As phosphoric esters ofhigher aliphatic alcohols, for example alkyl ether phosphoric acid suchas lauryl ether phosphoric acid, stearyl ether phosphoric acid, oleylether phosphoric acid; dialkyl ether phosphoric acid; alkyl phenyl etherphosphoric acid; dialkyl phenyl ether phosphoric acid; alkyl etherphosphoric acid salts such as sodium oleyl ether phosphate, potassiumstearyl ether phosphate are taken.

As nonionic surfactants, for example alkylol amides such as coconut oilfatty acid monoethanol amide, lauric acid diethanol amide and the like;polyoxyalkyl phenyl ethers such as polyoxyethlene alkyl phenyl ether andthe like; polyoxyethylene alkyl ether such as polyoxyethylene laurylether and the like; polyethylene glycol fatty acid esters such asdistearic acid polyethylene glycol and the like; sorbitan fatty acidesters such as monocapric acid sorbitan, monostearic acid sorbitan,distearic acid sorbitan and the like; polyoxyethylene sorbitan fattyacid ester such as monostearic acid polyoxyethylene sorbitan and thelike; polyoxyethylene sorbit fatty acid ester, polyoxyethylenepolyoxypropylene alkyl ethers, glycol ethers and so on are taken.

As cationic surfactants, for example alkyl trimethyl ammonium salts suchas lauryl trimethyl ammonium chloride, cetyl trimethyl ammonium bromide,stearyl trimethyl ammonium chloride and the like; alkyl dimethylbenzylammonium salts such as stearyl dimethylbenzyl ammonium chloride,benzalkonium chloride, lauryl dimethylbenzyl ammonium chloride and thelike are taken.

As amphoteric surfactants, for example alkyl betaine such as coconut oilalkylbetaine and the like; alkylamide betaine such as lauryldimethylamino acetic acid betaine and the like; imidazoline such asZ-alkyl-N-carboxymethyl-N-hydroxyethylimidazolium betaine; glycines suchas polyoctylpolyaminoethyl glycine and the like are taken.

As coupling agent, for example silane coupling agent, aluminum couplingagent, titanium coupling agent, zirconium coupling agent and the likeare taken.

One or more of the above coating agents may be used in the presentinvention.

The amount added of the coating agent is 0.1˜10% by weight, preferably0.5˜6% by weight. The amount less than 0.1% by weight gives a baddispersibility. When the amount exceeds 10% by weight the effect issufficient but it is not economically advantageous.

The surface treatment may be easily conducted by either dry or wetmethod according to the conventional method.

Second feature of the present invention lies in an agricultural filmwherein the above infrared absorber is incorporated and the process ofits preparation. The agricultural film of the present invention may beprepared by the method as stated below.

First, a resin and the infrared absorber of the present invention areadded in a mixer such as a ribbon blender, a Banbury mixer, a supermixeror a Henschel mixer and mixed, and thereafter melt-kneaded with anextruder, Banbury mixer or pressure kneader according to theconventional method.

The amount of the infrared absorber to be used may be preferably 1˜50parts by weight, more preferably 1˜20 parts by weight based on 100 partsby weight of the resin.

When it is less than 1 part by weight, the absorption of infrared raysis not sufficient. On the other hand, when it exceeds 50 parts byweight, light transmittance and mechanical strength required for anagricultural film are lowered.

Examples of the resin include polyhalogenated vinyl such as polyvinylchloride, polyvinylidene chloride; halogenated polyethylene, halogenatedpolypropylene, copolymers comprising combination of vinyl chloride-vinylacetate, vinyl chloride-ethylene, vinyl chloride-propylene, vinylchloride-styrene, vinyl chloride-isobutylene, vinyl chloride-vinylidenechloride, vinyl chloride-styrene-acrylonitrile, vinylchloride-butadiene, vinyl chloride-propylene chloride, vinylchloride-vinylidene chloride-vinyl acetate, vinyl chloride-maleic acidester, vinyl chloride-methacrylic acid ester, vinylchloride-acrylonitrile; polymers or copolymers of olefins such asethylene, propylene, butene-1, vinyl acetate and the like; polyethylenessuch as LLPE, LDPE and the like; polypropyrene; ethylene-α-olefincopolymer such as ethylene-propylene copolymer, ethylene-butene-1copolymer, ethylene-4-methyl-1-pentene copolymer, ethylene-hexenecopolymer and the like; ethylene-vinyl acetate copolymer,ethylene-acrylic acid copolymer, ethylene-methyl methacrylate copolymer,ethylene-vinyl acetate-methyl methacrylate copolymer, ionomer resin andthe like. Among these resins, polyethylene, ethylene-α-olefin copolymer,ethylene-vinyl acetate copolymer having less than 25% by weight of vinylacetate content are preferred in considering the aspects oftransparency, weathering resistance and price.

The resin composition prepared by mixing, melting and kneadingoperations may be shaped into a film e.g. an agricultural film accordingto the conventional method e.g. inflation, calendering or T-dieextrusion.

One side or both sides of the film may be provided with another resinlayer to prepare a multilayer film. This multilayer film can be preparedby a lamination such as dry lamination or heat lamination or acoextrusion such as T-die coextrusion or inflation coextrusion.

For preparation of the agricultural film of the present invention, theremay be added according to the necessity various kinds of the resinadditives used conventionally such as a plasticizer, a lubricant, alight stabilizer, an antioxidant, an antistatic agent, a pigment, anultraviolet absorber, an anti-fogging agent, an anti-haze agent, athermal stabilizer, an anti-blocking agent, a dye, a heat insulatingagent and the like.

Examples of plasticizers include low molecule weight of polyhydricalcohol plasticizers such as glycerin, ethylene glycol, triethyleneglycol, sorbitol and the like; phthalic ester plasticizers such asdioctyl phthalate (DOP), dimethyl phthalate and the like; phosphoricester plasticizers, paraffin plasticizers, wax plasticizers and thelike. Among these, polyhydric alcohols have anti-fogging action towardfilm, too.

Exampls of lubricants include fatty acids such as stearic acid, oleicacid, palmitic acid and the like; metal salts thereof; fatty acid amidederived from above fatty acids; waxes such as polyethylene wax and thelike, liquid paraffin, ester such as glycerin fatty acid ester andhigher alcohols.

Examples of light stabilizers include hindered amines, cresols,melamines, benzoic acid and the like.

Examples of hindered amine light stabilizers include2,2,6,6-tetramethyl-4-piperidylstearate,1,2,2,6,6-pentamethyl-4-piperidylstearate,2,2,6,6-tetramethyl-4-piperidinylbenzoate,N-(2,2,6,6-tetramethyl-4-piperidyl) dodecyl succinic acid imide,1-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyloxyethyl-2,2,6,6-tetramethyl-4-piperidyl(3,5-di-tert-butyl-4-hydroxyphenyl)propionate,bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate,bis(1,2,2,6,6-pentamethyl-4-piperidyl)-2-butyl-2-(3,5-di-tert-butyl-4-hydroxybenzyl)maloate,N,N′-bis(2,2,6,6-tetramethyl-4-piperidyl)hexamethylenediamine,tetra(1,2,2,6,6-pentamethyl-4-piperidyl)butanetetracarboxylate,tetra(2,2,6,6-tetramethyl-4-piperidyl)butanetetracarboxylate,bis(1,2,2,6,6-pentamethyl-4-piperidyl)di(tridecyl)butanetetracarboxylate, bis(2,2,6,6-tetramethyl-4-piperidyl)di(tridecyl)butanetetracarboxylate,3,9-bis{1,1-dimethyl-2-[tris(2,2,6,6-tetramethyl-4-piperidyloxycarbonyloxy)butylcarbonyloxy]ethyl}-2,4,8,10-tetraoxaspiro[5,5]undecane,3,9-bis{1,1-dimethyl-2-[tris(1,2,2,6,6-tetramethyl-4-piperidinyloxycarbonyloxy)butylcarbonyloxy]ethyl}-2,4,8,10-tetraoxaspiro[5,5]undecane,1,5,8,12-tetrakis{4,6-bis[N-(2,2,6,6-tetramethyl-4-piperidyl)butylamino]-1,3,5-triazine-2-yl}-1,5,8,12-tetrazadodecane,1-(2-hydroxyethyl)-2,2,6,6-tetramethyl-4-piperidinol/succinic aciddimethyl ester condensate,2-tert-octylamino-4,6-dichloro-s-triazine/N,N′-bis(2,2,6,6-tetramethyl-4-piperidyl)hexamethylenediaminecondensate, N,N′-bis(2,2,6,6-tetramethyl-4-piperidyl)hexamethylenediamine/dibromoethane condensate and the like.

It is suitable that the amount of the light stabilizers to beincorporated is 0.02 to 5 parts by weight per 100 parts by weight ofresins. The use of too small amount does not exert the effect, while theuse of too large amount impairs the transparency of the film.

As antioxidants, phenol, phosphorus, sulfur containing ones may betaken.

Examples of phenolic antioxidants include 2,6-di-tert-butyl-p-cresol,2,6-diphenyl-4-octadecyloxylphenol,stearyl(3,5-di-tert-butyl-4-hydroxyphenyl)propionate,distearyl(3,5-di-tert-butyl-4-hydroxybenzyl)phosphate, thiodiethyleneglycol bis[(3,5-di-tert-butyl-4-hydroxyphenyl)propionate],1,6-hexamethylene bis[(3,5-di-tert-butyl-4-hydroxyphenyl)propionate],1,6-hexamethylene bis[(3,5-di-tert-butyl-4-hydroxyphenyl)propionamide],4,4′-thiobis(6-tert-butyl-m-cresol), 2,2′-methylenebis(4-methyl-6-tert-butylphenol), 2,2′-methylenebis(4-ethyl-6-tert-butylphenol),bis[3,3-bis(4-hydroxy-3-tert-butylphenyl)butyric acid]glycol ester,4,4′-butylidene bis(6-tert-butyl-m-cresol), 2,2′-ethylidenebis(4,6-di-tert-butylphenol), 2,2′-ethylidenebis(4-sec-butyl-6-tert-butylphenol),1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane,bis[2-tert-butyl-4-methyl-6-(2-hydroxy-3-tert-butyl-5-methylbenzyl)phenyl]terephthalate,1,3,5-tris(2,6-dimethyl-3-hydroxy-4-tert-butylbenzyl)isocyanurate,1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)isocyanurate,1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-2,4,6-trimethylbenzene,1,3,5-tris[(3,5-di-tert-butyl-4-hydroxyphenyl)propionyloxyethyl]isocynurate,tetrakis[methylene-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]methane,2-tert-butyl-4-methyl-6-(2-acryloyloxy-3-tert-butyl-5-methylbenzyl)phenol,3,9-bis{1,1-dimethyl-2-[(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl}-2,4,8,10-tetraoxaspiro[5,5]undecane,triethylene glycolbis[(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate] and the like.

Examples of phosphorus antioxidants include tris (nonylphenyl)phosphite, tris(2,4-di-tert-butylphenyl) phosphite, tris[2-tert-butyl-4-(3-tert-butyl-4-hydroxy-5-methylphenylthio)-5-methylphenyl]phosphite,tridecyl phosphite, octyl diphenyl phosphite, di(decyl)monophenylphosphite, monodecyl diphenyl phosphite, mono(dinonylphenyl) bis(nonylphenyl)phosphite, di(tridecyl) pentaerythritol diphosphite,distearyl pentaerythritol diphosphite, di(nonylphenyl)pentaerythritoldiphosphite, bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite,bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphite,tetra(tridecyl)isopropylidenediphenyl diphosphite,tetra(tridecyl)isopropylidenediphenyl diphosphite, tetra(c₁₂₋₁₆ mixedalkyl)-4,4′-n-butylidene bis(2-tert-butyl-5-methylphenol)diphosphite,hexa(tridecyl)-1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butanetriphosphite, tetrakis(2,4-di-tert-butylphenyl)biphenylene diphosphite,2,2′-methylene bis(4,6-di-tert-butylphenyl)(octyl)phosphite and thelike.

Examples of sulfur-containing antioxidants includedialkyldithiopropionate such as dilauryl, dimyristyl or distearyl esterof thiodipropionic acid; β-alkylmercaptoprop ionic acid ester of polyolsuch as tetra(β-dodecylmercaptopropionate) of pentaerithrytol.

It is suitable that the amount of the above antioxidants to beincorporated is about 0.01˜3%.

As antistatic agents, there may be taken polyoxyethylene alkylamine,polyglycol ether, nonionic active agent, cationic active agent and soon.

As pigments, ones having a high transmittance are preferable.

As ultraviolet absorbers, there may be taken benzophenones,benzotriazoles, salicylic acid esters, substituted oxanilides,cyanoacrylates and the like.

Examples of benzophenones include 2-hydroxybenzopheno nes such as2,4-dihydroxylbenzophenone, 2-hydroxy-4-methoxybenzophenone,2-hydroxy-4-octoxybenzophenone, 5,5′-methylenebis(2-hydroxy-4-methoxy)benzophenone and the like.

Examples of benzotriazoles include 2-(2′-hydroxy-phenyl)benzotriazolessuch as 2-(2′-hydroxy-5′-methylphenyl) benzotriaozole,2-(2′-hydroxy-3′,5′-di-tert-butylphenyl) benzotriazole,2-(2′-hydroxy-3′,5′-di-tert-butylphenyl)-5-chlorobenzotriazole,2-(2′-hydroxy-3′-tert-butyl-5′-methylphenyl)-5-chlorobenzotriazole,2-(2′-hydroxy-5′-tert-octylphenyl)benzotriazole,2-(2′-hydroxy-3′,5′-dicumylphenyl)benzotriazole,2,2′-methylenebis(4-tert-octyl-6-benzotriazole)phenol and the like.

Examples of salicylic acid esters include benzoates such asphenylsalicylate, resorcinol monobenzoate,2,4-di-tert-butylphenyl-3′,5′-di-tert-butyl-4′-hydroxybenzoate,hexadecyl-3,5-di-tert-butyl-4-hydroxybenzoate and the like.

Examples of substituted oxanilides include 2-ethyl-2′-ethoxyoxanilide,2-ethoxy-4′-dodecyloxanilide and the like.

Examples of cyanoacrylates include ethyl-α-cyano-,β,β-diphenyl acrylate,methyl-2-cyano-3-methyl-3-(p-methoxyphenyl)acrylate and the like.

As anti-fogging agents, there may be preferably employed nonionic,anionic and cationic surfactants.

Specifically, sorbitan fatty acid esters such as sorbitan monostearate,sorbitan monopalmitate, sorbitan monobehenate and the like, glycerinfatty acid esters such as glycerin monolaurate, glycerin monostearate,glycerin monopalmitate, diglycerin dilaurate, diglycerin distearate,diglycerin monopalmitate, triglycerin monostearate and the like,polyhydric alcohol surfactants including polyethylene glycol activeagents such as polyethylene glycol monostearate, their alkylene oxideadducts, polyoxyalkylene ether, organic acid esters of sorbitans orglycerins may be taken.

As anti-haze agents, fluorine or silicone ones which have beenconventionally used for agricultural film of polyolefin resins may beincorporated. It is preferable to use for example, low or high moleculecompounds containing perfluoroalkyl or perfluoroalkenyl group which haveat least 0.01% by weight of solubility in water and an ability to lowersurface tension of water to below 35 dyn/cm preferably 30 dyn/cm at 25°C. Also, perfluoroalkyl group may be one containing an oxygen atom inthe carbon chains.

Examples of fluorine surfactants include commercially available products“Unidyne DS-401”, “Unidyne DS-403”, “Unidyne DS-451” (Products of DaikinIndustries Ltd.), “Megafac F-177” (product of Dainippon Ink & ChemicalsIncorporated), “Florard FC-170”, “Florard FC-176”, “Florard FC-430”(products of Sumitomo 3M Ltd.), “Sarflone S-141”, “Sarflone S-145”,“Sarflone S-381”, “Sarflone S-382, “Sarflone S-393” (products of AsahiGlass Co., Ltd.).

Examples of silicone anti-haze agents include polyether modifiedsilicone oil, carboxy modified silicone oil and carbinol modifiedsilicone oil and amino modified silicone oil. In general, ones arepreferred which have at least 0.1% by weight of solubility in water andan ability to lower surface tension of water to below 35 dyn/cm at 25°C.

Examples of commercially available silicone surfactants include “KF-354”(a product of Shin-Etsu Chemical Co., Ltd.), “SH-3746” (a product of DowCorning Toray Silicone Co., Ltd.) “TSF-4445” (a product of ToshibaSilicone Co., Ltd.). The anti-haze agents may be preferably incorporatedin an amount of about 0.1˜5% per 100 perts by weight of resins.

As thermal stabilizers, especially tin stabilizers, lead stabilizers,complex metal fatty acid stabilizers such as calcium-zinc, barium-zincwhich are incorporated in vinyl chloride resins may be taken.

Also, other heat insulation agents, magnesium carbonate, magnesiumsilicate, silicon dioxide, aluminum oxide, barium sulfate, calciumsulfate, magnesium hydroxide, aluminum hydroxide, calcium hydroxide,phosphate, silicate, hydrotalcite may be employed to such extent thatthey do not impair the transparency of film.

One or more of the above various additives may be properly selected forincorporation. The amount of the additives to be incorporated may besuch range that it causes no deterioration in the property of the film.It is not restricted particularly so long as it is within such range.

The agricaltural films of the present invention are 1) one which ischaracterized by incorporating 1˜50 parts by weight of the complexhydroxide salt of the present invention into 100 parts by weight of aresin, 2) one which is characterized by incorporating 1˜50 parts byweight of the complex hydroxide salt of the present invention and 0.02˜5parts by weight of a hindered amine light stabilizer into 100 parts byweight of a resin, 3) one which is characterized by incorporating 1˜50parts by weight of the complex hydroxide salt of the present inventionand 0.02˜5 parts by weight of an anti-fogging agent into 100 parts byweight of a resin, and 4) one which is characterized by incorporating1˜50 parts by weight of the complex hydroxide salt of the presentinvention and 0.02˜5 parts by weight of an anti-haze agent into 100parts by weight of a resin.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an infrared absorption spectrum of the agricultural filmwherein 5 parts by weight of the infrared absorber obtained in Example 3were incorporated.

FIG. 2 is an infrared absorption spectrum of the agricultural filmwherein 10 parts by weight of the infrared absorber obtained in Example3 were incorporated.

FIG. 3 is an infrared absorption spectrum of the agricultural filmwherein 5 parts by weight of the infrared absorber obtained in Example 4were incorporated.

BEST MODES FOR CARRYING OUT THE INVENTION

The following examples illustrate the present invention morespecifically.

The BET specific surface area can be measured from the amount adsorpedof nitrogen according to the conventional a method. The secondaryparticle size can be determined by a method which comprises addingsample powder to an organic solvent such as ethanol or n-hexane,dispersing by ultrasonic, dropping the dispersion on a sample mount fora microscope and observing under a microscope. An electron microscope,an optical microscope and so on can be used as the microscope.

EXAMPLE 1

Water was added to a mixture of 214.0 g of powdery aluminum hydroxidecontaining 65% by weight of Al₂O₃, 13.9 g of magnesium carbonatecontaining 42.0% by weight of MgO and 45.2 g of lithium carbonate tomake 3 liters (L) of slurry in the total volume.

This slurry was subjected to heat treatment in 5 L of an autoclave at150° C. for 4 hours. While the temperature of the slurry was kept to 80°C., 11.5 g of sodium stearate was added to carry out surface-treatment.Thereafter, the slurry was filtered to form a cake under reducedpressure with a Buchner funnel, and the cake was washed with a quantityof water equivalent to about 50 times of the Al₂O₃ content in weight.After washing, the cake was dried overnight at approximately 110° C. toyield 300 g of white powders.

The obtained white powders were subjected to chemical analysis. As theresult, it had the composition of[Al₂(Li_(0.90).Mg_(0.10))(OH)₆]₂(CO₃)_(1.10).3.0H₂O. It had a BETspecific surface area of 18.0 m²/g, an average particle size of 0.85 μmand a refractive index of 1.53.

EXAMPLE 2

Water was added to a mixture of 214.0 g of powdery aluminum hydroxidecontaining 65% by weight of Al₂O₃, 13.9 g of magnesium carbonatecontaining 42.0% by weight of MgO, 15.7 g of magnesium hydroxide and45.2 g of lithium carbonate to make 3 L of slurry in the total volume.

This slurry was subjected to heat treatment in 5 L of an autoclave at150° C. for 4 hours. While the temperature of the slurry was kept to 80°C., 11.5 g of sodium stearate was added to carry out surface-treatment.Thereafter, the slurry was filtered to form a cake under reducedpressure with a Buchner funnel, and the cake was washed with a quantityof water equivalent to about 50 times of the Al₂O₃ content in weight.After washing, the cake was dried overnight at approximately 110° C. toyield 320 g of white powders.

The obtained white powders were subjected to chemical analysis. As theresult, it had the composition of[Al₂(Li_(0.90).Mg_(0.30))(OH)_(6.4)]₂(CO₃)_(1.10).3.0H₂O. It had a BETspecific surface area of 22.4 m²/g, an average particle size of 1.05 μmand; a refractive index of 1.53.

EXAMPLE 3

The aluminum lithium magnesium complex hydroxide salt obtained inExample 2 was burned for a hour 210° C. to remove water contained in itand used as an infrared absorber to prepare an agricultural film, andthe effectiveness was confirmed.

This infrared absorber was added in amounts of 5, 7.5 and 10 parts to100 parts by weight of LDPE resin, and the respective mixtures wereformed into pellets at about 200° C. using a double-screw extruder. Thepellets were extruded through T-die to obtain agricultural film having100 μm in thickness. The transparency and heat insulating effect of thisagricultural film were measured. The heat insulating property wasevaluated by measuring the infrared absorptivities of the obtained filmat intervals of 20 cm⁻¹ in the wavelength range of 2000 cm⁻¹˜400 cm⁻¹,and each measurement obtained was multiplied and the average of theobtain products was evaluated as a heat insulation efficiency. Thegreater the heat insulation efficiency, the greater the heat insulatingeffect.

The transparency was evaluated in transmittance percent to the totallight of 700˜400 nm which was measured using a spectrophotometer (aproduct of Japan Spectroscopic Co., Ltd.). The infrared absorptionspectrum of the film wherein 5 parts by weight of the infrared absorberwere incorporated is shown in FIG. 1 and that of the film wherein 10parts by weight of the infrared absorber were incorporated is shown inFIG. 2. Also, the heat insulation efficiency and the total lighttransmittance percent (%) are shown in table 1.

EXAMPLE 4

100 parts by weight of polyvinyl chloride (degree of polymerization:1300), 0.2 part by weight of zinc stearate, 0.2 part by weight ofdibenzoylmethane, 10 parts by weight of the complex hydroxide obtainedin Example 1 and 50 parts by weight of DOP were used, roll-milled at170° C. and pressed to obtain an agricultural film having a thickness of100 μm. The heat insulation efficiency and the total light transmittanceof this agricultural film are shown in table 1.

EXAMPLE 5

To ethylene-vinyl acetate copolymer (14% by weight of vinyl acetatecontent and 0.92 g/cm³ of density), were added 10.0% by weight ofinfrared absorber the compound obtained in Example 2 , 0.5% by weight ofhindered amine light stabilzer “TINUVIN 622-LD” (a trade nama, a productof Ciba Geigy Co., Ltd.), 0.2% by weight of an antioxidant (“Irganock” atrade name, a product of Ciba Geigy Co., Ltd.), 1.0% by weight ofmonoglycerin monostearate, 1.0% by weight of diglycerin distearate asanti-fogging agent, 0.1% by weight of anti-haze agent “Unidyne DS-401”(a product of Daikin Industries Ltd.) and 0.2% by weight of lubricantstearylamide to become 100% in the total, mixed for 5 minutes 130° C.with a Banbury mixer and granulated with a granulating machine to obtainpellets of composition. They are designated as the resin composition A.Next, pellets of composition B were obtained in a similar manner exceptthat no infrared absorber was added. The resin composition A was set asan intermediate layer while the resin composition B as both the outerlayers to prapare a film having a thickness of 0.1 mm (0.06 mm of theintermediate layer and 0.02 mm of each outer layer) with an inflationfilm making machine, and the obtained film was subjected to outdoorexposure in the stretched state for 8 months of from April to November,1995 under the condition of which its weathering resistance,anti-fogging property and anti-haze property were evaluated according tothe following manners:

Weathering resistance was made by visual inspection, and thediscoloration (yellowing and browning) and deterioration of film werechecked. Also, an elongation test was conducted according to JIS K-6781to measure the retention (%) of elongation, and the retention of 90% ormore was evaluated to cause no deterioration.

Anti-fogging property was made by visual inspection, the formation ofwater droplets on the film was checked through the overall observationof it.

Anti-haze property was made by visual inspection, and the formation ofhaze on the film was checked through the overall observation of it.

As a result, all the agricultural films obtained in Examples involvingin the present invention were found to have no problem with respect tothe weathering resistance (neither discoloration nor deterioration offilm was recognized), the anti-fogging property (there was no place toform droplet) and the anti-haze property (no haze generation isrecognized).

EXAMPLE 6

Water was added to a mixture of 13.9 g magnesium carbonate containing42.0% by weight of MgO, 15.7 g of magnesium hydroxide, 214.0 g ofpowdery aluminum hydroxide containing 65% by weight of Al₂O₃ and 53.2 gof lithium carbonate to make 3 L of slurry in total volume. The slurrywas subjected to heat treatment in 5 l of an autoclave at 150° C. for 4hours. After the heat treatment, to the slurry cooled to 25° C. wasadded 5% by weight of sulfuric acid (molar ratio of H₂SO₄/Al₂O₃=0.75)thereby effecting acid treatment. And then, 4 liters of aqueous solutioncontaining 123.6 g sodium silicate (No.1 water glass, 36.5% by weight interms of SiO₂) was added and agitated for 60 minutes. While thetemperature of the slurry was kept to 50° C., 11.5 g of stearyl etherphosphoric acid was added to carry out surface-treatment. Thereafter,the slurry was filtered to form a cake under reduced pressure with aBuchner funnel, and the cake was washed with a quantity of waterequivalent to about 50 times of the Al₂O₃ content in weight. Afterwashing, the cake was dried overnight at about 110° C. to obtain 380 gof white powder.

The obtained white powder was subjected to chemical analysis. As theresult, it had the composition of[Al₂(Li_(0.90).Mg_(0.30)(OH)_(6.4)]₂(SiO₂)_(1.10).3.0H₂O.

It had a BET speific surface area of 12.5 m²/g, an average particle sizeof 0.7 μm and a refractive index of 1.50.

This white powder was dried at 200° C. for 3 hours to obtain onecontaining 0.3 mole of water (3 hours-burned product) was subjected tothe agricultural film-preparing test as after-mentioned.

EXAMPLE 7

The complex hydroxide salt obtained in Example 6 was burned for a hourat 210° C. and was added in amounts of 5, 7.5 and 10 parts by weight toobtain film in similar manner as in Example 3. The heat insulationefficiency and the total light transmittance percent (%) are shown intable 1.

COMPARATIVE EXAMPLE 1

Water was added to a mixture of 214.0 g of powdery aluminum hydroxidecontaining 65% by weight of Al₂O₃ and 55.0 g of lithium carbonate tomake 3 L of slurry in the total volume.

This slurry was subjected to heat treatment in 5 L of an autoclave at150° C. for 4 hours. While the temperature of the slurry was kept to 80°C., 11.5 g of sodium stearate was added to carry out surface-treatment.Thereafter, the slurry was filtered to form a cake under reducedpressure with a Buchner funnel, and the cake was washed with a quantityof water equivalent to about 50 times of the Al₂O₃ content in weight.After washing, the cake was dried overnight at approximately 110° C. toyield 300 g of white powders.

The obtained white powders were subjected to chemical analysis. As theresult, it had the composition of [Al₂Li(OH)₆]₂(CO₃).3.0H₂O. It had aBET specific surface area of 8.5 m²/g, an average particle size of 1.0μm and a refractive index of 1.55.

COMPARATIVE EXAMPLE 2

The infrared absorber obtained in Comparative Example 1 was used tomeasure the heat insulation efficiency and the total light transmittancepercent (%) of the agriculcural film in a similar manner as in Example3. The results were as shown in table 1.

TABLE 1 Amount Heat Total Light Incorporated Insulation TransmittanceNo. (PHR) Efficienty Percent (%) Example 3 5.0 46.90 85.20 (LDPE) 7.552.84 83.18 10 55.24 80.14 Control 0 25.44 94.11 (LDPE) Example 4 5.065.21 91.03 (PVC) Control 0 60.18 96.02 (PVC) Example 7 5.0 48.5 85.307.5 54.2 83.21 10 56.85 80.25 Comparative 5.0 43.01 73.73 Example 2 7.547.25 62.19 (LDPE) 10 51.03 60.34

INDUSTRIAL APPLICABILITY

The infrared absorber composed of the complex hydroxide salt of thepresent invention has a high ability to absorp infrared rays, anexcellent dispersibility with the resins and a refractive index close tothat of the resin so that it is easily incorporated in the resin andresin processing is facilitated, and the shaped film therefrom isexcellent in the heat insulation property and transparency so that it issuitable as an agricultural film.

What is claimed is:
 1. An infrared absorber which is characterized bycontaining as an ingredient a hydroxide complex salt represented by theformula: (Al₂(Li_((1−x)).M²⁺_((x+y))(OH)_((6+2y)))_(n)(A^(n−))_((1+x)).mH₂O; wherein M²⁺ is adivalent metal, A^(n−), is an anion having a valence of n; and m, x andy are numbers respectively in the ranges of 0≦m<5, 0.01≦x≦0.5 and0≦y≦0.5.
 2. An infrared absorber wherein the hydroxide complex salt asclaimed in claim 1 is coated with one or more of compounds selected froma group consisting of higher fatty acids, higher fatty acid salts,esters of higher aliphatic alcohol and phosphoric acid, waxes, nonionicsurfactants, cationic surfactants and coupling agents.
 3. Anagricultural film comprising per 100 parts by weight of a resin: 1 to 50parts by weight of the hydroxide complex salt as claimed in claim
 1. 4.An agricultural film comprising per 100 parts by weight of a resin: 1 to50 parts by weight of the hydroxide complex salt as claimed in claim 1;and 0.02 to 5 parts by weight of a hindered amine light stabilizer. 5.An agricultural film comprising per 100 parts by weight of a resin: 1 to50 parts by weight of the hydroxide complex salt as claimed in claim 1;and 0.02 to 5 parts by weight of an anti-fogging agent.
 6. Anagricultural film comprising per 100 parts by weight of a resin: 1 to 50parts by weight of the hydroxide complex salt as claimed in claim 1; and0.02 to 5 parts by weight of an anti-haze agent.
 7. An agricultural filmcomprising per 100 parts by weight of a resin: 1 to 50 parts by weightof the hydroxide complex salt as claimed in claim
 2. 8. An agriculturalfilm comprising per 100 parts by weight of a resin: 1 to 50 parts byweight of the hydroxide complex salt as claimed in claim 2; and 0.02 to5 parts by weight of a hindered amine light stabilizer.
 9. Anagricultural film comprising per 100 parts by weight of a resin: 1 to 50parts by weight of the hydroxide complex salt as claimed in claim 2; and0.02 to 5 parts by weight of an anti-fogging agent.
 10. An agriculturalfilm comprising per 100 parts by weight of a resin: 1 to 50 parts byweight of the hydroxide complex salt as claimed in claim 2; and 0.02 to5 parts by weight of an anti-haze agent.